Background:The central nervous system depends on thyroid hormones for the growth and upkeep of normal physiological processes. The preferred medication for thyroid replacement therapy continues to be levothyroxine, a synthetic thyroid hormone.Aim: The current study used morphometric analysis to evaluate the effects of levothyroxine on the postnatal development of albino rats' visual cortex following artificially inducing maternal hypothyroidism. Materials and Methods: Eighteen (18) pregnant rats were randomly categorized into 3 equal groups (GI, GII &GIII). GI is the control group, which received distilled water orally every day from the first day of gestation until day 20 after delivery. GII is the hypothyroid group, which received carbimazole (CM) orally in a dose of 5 mg/rat/day from the first day of gestation until day 20 after delivery. Finally, GIII is the hypothyroid group treated with levothyroxine (LT). GIII received CM orally in a dose of 5 mg/rat/dayfrom the 1st day of pregnancy until 20 days after delivery, along with LT subcutaneously at a dose of 5 g/day/rat). Brains of the rats' offspring at newborn, postnatal 10th day, and postnatal 20th day old were processed for morphometric analysis. Results: The present study revealed a significant decrease in the mean nuclear diameter of the pyramidal cells in layer IV between hypothyroid and age-matched control rats and an increase in the mean nuclear diameter of layer IV pyramidal cells after treatment with Levothyroxine toward the normal values. The numerical density of pyramidal cells in layer IV in the present study increased significantly in hypothyroid rats in comparison with their age-matched controls. These insults were ameliorated in hypothyroid rats treated with Levothyroxine. Conclusion: Levothyroxine might protect against maternal hypothyroidism-induced visual cortical neurotoxicity in neonatal rats.